Scalar function in LinqToSql
-
06-09-2019 - |
Question
In ADO.Net/SQLClient I would often do something like this:
SELECT COUNT(*) FROM SomeTable WHERE SomeKey = 1234
...and fire it using executescalar to return the value of count - for a simple check if something exists.
How would I do the same using LinqToSql?
Solution
if (context.SomeTable.Any(row => row.SomeKey == 1234))
{
DoStuff();
}
You could also use Count()
.
if (context.SomeTable.Count(row => row.SomeKey == 1234) > 0)
{
DoStuff();
}
But this requires always to go through all rows while Any()
can return after the first matching row - so Any()
might have better performance.
OTHER TIPS
Remember, Linq to Sql is deferred execution, which means, the query only actually executes when you access the collection. Therefore:
var q = (from p in db.SomeTable
where p.SomeKey == 1234
select p).Count();
Will turn into a SELECT Count() on the SQL side of things.
If you're looking to see if something exists you can use the any function:
if (context.SomeTable.Any(i => i.SomeKey == 1234))
{
return true;
}
or if you actually want to know that count you can use the where function and the count function:
context.SomeTable.Where(i=> i.SomeKey == 1234).Count();